Yet Another...5F2A Tweed Princeton build

[keithb7]

Charisjapan, yes that is an extension jack on the tweed deluxe. The cab was built by Memphis Amps as you know. There is a bit of a story behind that cab.
I was looking to build my first amp and I found, what appeared to be a near new, used TD cab for sale in the classified section of a different forum. Seller also had a matching tweed bottom cab. It all looked awesome. I had no idea who built it, but the price was excellent so I immediately bought it. However I only bought the combo and not the bottom cab. When it arrived I was very impressed with the cab an contacted to seller to find out who built it. I had never heard of the builder who was Bruce at Memphis Amps. I assume the previous owner had the jack installed. It arrived like that. I can't answer your questions about the wiring. My understanding is the OT on the tweed deluxe is 8 ohm. I run an 8 ohm C12N speaker. If you want to run an extension speaker too, you need to make sure the amp only sees 8 ohm total, I believe. So 2, 16 ohm speakers I guess. In the end when I wanted to build my 5F2A, I immediately contacted Memphis amps to custom build me the cab I wanted. Once again I was no let down, it's a beautiful cab as Bruce does a great job.

Best of luck with your cab. If you like I can take a photo with more detail on the jack, for you. - Keith

[charisjapan]

Originally Posted by keithb7

Charisjapan, yes that is an extension jack on the tweed deluxe. The cab was built by Memphis Amps as you know. There is a bit of a story behind that cab.
I was looking to build my first amp and I found, what appeared to be a near new, used TD cab for sale in the classified section of a different forum. Seller also had a matching tweed bottom cab. It all looked awesome. I had no idea who built it, but the price was excellent so I immediately bought it. However I only bought the combo and not the bottom cab. When it arrived I was very impressed with the cab an contacted to seller to find out who built it. I had never heard of the builder who was Bruce at Memphis Amps. I assume the previous owner had the jack installed. It arrived like that. I can't answer your questions about the wiring. My understanding is the OT on the tweed deluxe is 8 ohm. I run an 8 ohm C12N speaker. If you want to run an extension speaker too, you need to make sure the amp only sees 8 ohm total, I believe. So 2, 16 ohm speakers I guess. In the end when I wanted to build my 5F2A, I immediately contacted Memphis amps to custom build me the cab I wanted. Once again I was no let down, it's a beautiful cab as Bruce does a great job.

Best of luck with your cab. If you like I can take a photo with more detail on the jack, for you. - Keith

Keith,

Thanks for the reply! Yeah, if it's not too much bother, I would like to see some closeups.

Now that I'm getting closer to my own build coming together, I want to answer a few nagging questions about those jacks.

1) I thought I remembered the green tip wire (as well as grid wires to the preamp tubes) being really sensitive to length and lead dress. I wondered how that worked with the connection of main speaker tipe to external speaker tip? That's assuming that the ground wires are not quite so critical.

2) On my cheapo combo, when you plug into the external jack, the main speaker cuts out. That way you don't have to worry about what the combination of the speakers' ohmage is, only the external. But yeah, if both work, you DO have to figure that in. hmmm...?

3) I got an OT that works with 4/8/16 ohms. Some builders use a 3-way rotary switch, but I was thinking of only needing 4 and 8 ohms, so just an A/B switch will work. Right?

I'll probably ask this same question on my build thread, but since you brought it up...

[keithb7]

Ever heard the saying, "Pride Comes Right Before A Fall"? Well I was feeling exceptionally proud of my power supply and transformer wiring tonight. Thanks to the helping members here, I finally hooked up all the PT wires. I used anchors and tight twists! Then right after gloating about it all, I burned the black power supply wire shown, and crushed the plastic in my indicator light while trying to tighten it down. Off tomorrow to find a new lamp assy. Oh well. She's coming along. Kinda like the old Pontiac commercials, I am starting to "Feel The Excitement!"

Should I get the red/yellow center tap wire from the PT away from the green twisted wires for the heaters? Will this create noise? See in pic.



Japan-man, I will post the pics and add my .02 on your build thread.

[keithb7]

Got the tone stack, jacks and ground strip done tonight. I don't like the look of the tone bleed capacitor. I cut it before I had a plan for the ground strip. Oh well. I used left over pieces of the ground strip to mount the main strip to the turrets while keeping it up for clearance. Also used pieces to mount to the input jacks. It feels good and is firmly in place. I checked all my grounds with a MM and all seems good. I hope it works well. Sure hope I don't have to take that main board out again any time soon!

[JBennett]

Looks real nice so far.

[hackworth1]

[QUOTE=keithb7;4184366]Ever heard the saying, "Pride Comes Right Before A Fall"? Well I was feeling exceptionally proud of my power supply and transformer wiring tonight. Thanks to the helping members here, I finally hooked up all the PT wires. I used anchors and tight twists! Then right after gloating about it all, I burned the black power supply wire shown, and crushed the plastic in my indicator light while trying to tighten it down. Off tomorrow to find a new lamp assy. Oh well. She's coming along. Kinda like the old Pontiac commercials, I am starting to "Feel The Excitement!"

Should I get the red/yellow center tap wire from the PT away from the green twisted wires for the heaters? Will this create noise? See in pic.

The way you have it is OK.

Is there a heater center tap?

Moot point now, but you can use that unused outside leg on the pilot light for a solder tab. It is connected internally to the opposing tab. It is the shell on the lamp assembly.

[hackworth1]

Originally Posted by keithb7

Got the tone stack, jacks and ground strip done tonight. I don't like the look of the tone bleed capacitor. I cut it before I had a plan for the ground strip. Oh well. I used left over pieces of the ground strip to mount the main strip to the turrets while keeping it up for clearance. Also used pieces to mount to the input jacks. It feels good and is firmly in place. I checked all my grounds with a MM and all seems good. I hope it works well. Sure hope I don't have to take that main board out again any time soon!

Hard to see clearly in the pic, but it looks like you have the inside jack's ground tab soldered by wire to the bus AND to the jack next door.

Only one ground is required. An extra ground creates a ground loop.

In the future (please take this in the spirit of brotherly love with fond regards and my best intentions!) use any other color wire other than green wire for hot side leads and hook ups.

[coldengray]

Why is green bad on that side?

[hackworth1]

Originally Posted by coldengray

Why is green bad on that side?

Not bad, per se. Green or black is customarily used for ground wiring.

Using contrasting colors helps others (and yourself) to see what's what.

[keithb7]

Thanks for the tips. I was scratching my head over the plethora of wire colors you provided Dave. I just picked on and ran wit it. There was plenty of green. I did change up a few colors on the tube side so I could trouble shoot if necessary. I will look into the ground loop you mentioned. Thanks.

[keithb7]

Dave I looked again at the Weber 5F2A layout, as shown here below. It shows the sleeve (G) of input 2 going to ground. On my amp I attached the ground strip to this point.

I also see that the switch, center lug of input 2 is going to input 1 tip. From there the signal goes through the 1 meg resistor, then to the sleeve (G) of tip 1 to ground. This tip, is supposed to go to ground, which I also connected to my grounding strip. You can see my grounding strip in my photo connected to input 1 and 2 as described. Did I create a ground loop? I thought that I wired mine as shown in the layout. Should I remove the wire from input 2 (S) connected to input 1 (T)? Thanks,

[hackworth1]

The two jacks make ground by virtue of the fact that - when bolted tightly - their bodies make direct contact with the chassis (unless some non conductive fibre washers are used to isolate them from the chassis).

Your ground bus is sending - anything connected to it - to ground (ground = 0 volts) via ONE input jack's ground lug (solder tab) .

The other input jack needs no connection to the ground bus...

BECAUSE it grounds itself to the chassis.

It is not a big deal. It will work the way you have it, but...

a small ground loop exists and it will cause some small noise. Perhaps inaudible to the human ear. Perhaps not.

Here's the essence of my proposition: Do not create unwanted noise when it is easy to avoid.

[keithb7]

Makes sense. Thanks Dave. I will remove the connection from ground buss to input 1, G tip, which is the input with the 1 meg resistor.

[gearjunkie]

Looking good Dave...bummer about the burnt lead but nothing a simple splice wont remedy...

what brand Resistors does Dave provides in his kits??

Not to hi-jack your thread at all but I noticed Charis-japan mentioned his primary speaker will wuit playing once the 2nd is plugged in and I wanted to show him this..Same thing happened to me on our forst 3 5E3 builds as per diagram..after feeling it wasn't acceptable to have this happening I ntoice there is an updated layout on the kits coming out of toronto

Here's how they used to set them up which causes one speaker to quit


Here's how they need to be wired to make them both work.NOTE impedance MUST BE an 8ohm load when plugged into both as with single..


Have a look at your current setup Charis and compare it to these photos..Cheers

[keithb7]

I plugged in my amp tonight for some testing. Pilot lamp works. No smoke. So far so good. Plugged in some tubes and turned it on. 12AX7 and 6V6 are glowing but the rectifier is not. No sound. Pulled the tubes and took some measurements around the PT. Here is what I get:

Measuring across the heater wires I get 7.2V AC
Red wires from PT: 400V AC
Yellow wires: 1 pin on first yellow wire, other to ground gets me 64V A/C. Other yellow wire and to ground gets me 62V. (kinda adds up to 120. Coincidence?) If I put a probe on each yellow wire and measure across I get 5.7V AC. I assume I am supposed to measure across both yellow wires to get 5.7V. Do these voltages seem ok?
Thanks.

[charisjapan]

Originally Posted by Ernie R

Looking good Dave...bummer about the burnt lead but nothing a simple splice wont remedy...

what brand Resistors does Dave provides in his kits??

Not to hi-jack your thread at all but I noticed Charis-japan mentioned his primary speaker will wuit playing once the 2nd is plugged in and I wanted to show him this..Same thing happened to me on our forst 3 5E3 builds as per diagram..after feeling it wasn't acceptable to have this happening I ntoice there is an updated layout on the kits coming out of toronto

Here's how they used to set them up which causes one speaker to quit


Here's how they need to be wired to make them both work.NOTE impedance MUST BE an 8ohm load when plugged into both as with single..


Have a look at your current setup Charis and compare it to these photos..Cheers

Ummm... Ernie?

Those look the same to me. They are both parallel, right? You would need an external switch with an isolate circuit switch. (I think)

The purpose, at least on my MIJ combo, is so that when you DO hook up an external speaker you don't have to change the internal speaker to get the correct ohms. If the internal/external speaker jacks are simply parallel or series, then you MUST have both speakers connected, OR have a 4/8 ohm switch and make sure to change if you unplug.

So, muddling through all this, I went to Switchcraft and found a spec chart for 39 different jacks!!

Jack Schematics WoWser!

I'm grasping the shunt, and now the 'make curcuit' and 'isolate circuit' idea (I think).

[charisjapan]

Originally Posted by keithb7

I plugged in my amp tonight for some testing. Pilot lamp works. No smoke. So far so good. Plugged in some tubes and turned it on. 12AX7 and 6V6 are glowing but the rectifier is not. No sound.

Keith,

Lamp on and no smoke is great, but no sound is a bummer!

We're rootin' for ya!

[Telenut62]

First of all are the yellow wires the HT secondary and red 5VAC? It looks like you have wired it reverse...Yellow pins 2-8 Red pins 4-6. I would try your readings first with no tubes...B+ should be around 420V or more.

[andyfromdenver]

[QUOTE=hackworth1;4185226]

Originally Posted by keithb7

Keithb7, unless this is an old pic or I am missing it, I don't see where your rectifier cathode (eight) is going into the power rail. But I would think you would still see a glow on the tube, hmm.

[andyfromdenver]

Also, maybe a q for the wizards around here, is it best practice if you have a ground buss bar to send your pots there vs. just soldering the lug to the back of the pot a' la dozens of years of major manufacturer's technique? I'm just curious, cause in my boothills 5e3 kit he gave me the bus bar which i've not used in any of my 3 builds.